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Date: Tue, 15 Aug 2023 15:20:30 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Dan Williams <dan.j.williams@...el.com>, linux-coco@...ts.linux.dev
Cc: Borislav Petkov <bp@...en8.de>,
Dionna Glaze <dionnaglaze@...gle.com>,
Brijesh Singh <brijesh.singh@....com>, peterz@...radead.org,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] virt: sevguest: Prep for kernel internal {get,
get_ext}_report()
On 8/14/23 02:43, Dan Williams wrote:
> In preparation for using the TSM key facility to convey attestation blobs
> to userspace, add an argument to flag whether @arg is a user buffer or a
> kernel buffer.
>
> While TSM keys is meant to replace existing confidenital computing
s/confidenital/confidential/
> ioctl() implementations for attestation report retrieval the old ioctl()
> path needs to stick around for a deprecation period.
>
> No behavior change intended, just introduce the copy wrappers and @type
> argument.
>
> Note that these wrappers are similar to copy_{to,from}_sockptr(). If
> this approach moves forward that concept is something that can be
> generalized into a helper with a generic name.
>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Cc: Dionna Glaze <dionnaglaze@...gle.com>
> Cc: Brijesh Singh <brijesh.singh@....com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
> drivers/virt/coco/sev-guest/sev-guest.c | 48 ++++++++++++++++++++++++-------
> 1 file changed, 37 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index 97dbe715e96a..f48c4764a7a2 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -470,7 +470,32 @@ static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code,
> return 0;
> }
>
> -static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
> +enum snp_arg_type {
> + SNP_UARG,
> + SNP_KARG,
> +};
> +
> +static unsigned long copy_from(void *to, unsigned long from, unsigned long n,
> + enum snp_arg_type type)
> +{
> + if (type == SNP_UARG)
> + return copy_from_user(to, (void __user *)from, n);
I'm a fan of blank lines to make reading functions easier. A blank line
here and below after the memcpy() would be nice.
Ditto in the copy_to() function.
> + memcpy(to, (void *)from, n);
> + return 0;
> +}
> +
> +static unsigned long copy_to(unsigned long to, const void *from,
> + unsigned long n, enum snp_arg_type type)
> +{
> + if (type == SNP_UARG)
> + return copy_to_user((void __user *)to, from, n);
> + memcpy((void *)to, from, n);
> + return 0;
> +}
> +
> +static int get_report(struct snp_guest_dev *snp_dev,
> + struct snp_guest_request_ioctl *arg,
> + enum snp_arg_type type)
You can go out to 100 characters now, so you can put "struct .. *arg" on
the top line and just put the enum on a new line.
> {
> struct snp_guest_crypto *crypto = snp_dev->crypto;
> struct snp_report_resp *resp;
> @@ -482,7 +507,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
> if (!arg->req_data || !arg->resp_data)
> return -EINVAL;
>
> - if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
> + if (copy_from(&req, arg->req_data, sizeof(req), type))
> return -EFAULT;
>
> /*
> @@ -501,7 +526,7 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io
> if (rc)
> goto e_free;
>
> - if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
> + if (copy_to(arg->resp_data, resp, sizeof(*resp), type))
> rc = -EFAULT;
>
> e_free:
> @@ -550,7 +575,9 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
> return rc;
> }
>
> -static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
> +static int get_ext_report(struct snp_guest_dev *snp_dev,
> + struct snp_guest_request_ioctl *arg,
> + enum snp_arg_type type)
Ditto here on the 100 characters.
> {
> struct snp_guest_crypto *crypto = snp_dev->crypto;
> struct snp_ext_report_req req;
> @@ -562,7 +589,7 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
> if (!arg->req_data || !arg->resp_data)
> return -EINVAL;
>
> - if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
> + if (copy_from(&req, arg->req_data, sizeof(req), type))
> return -EFAULT;
>
> /* userspace does not want certificate data */
> @@ -611,14 +638,13 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
> if (ret)
> goto e_free;
>
> - if (npages &&
> - copy_to_user((void __user *)req.certs_address, snp_dev->certs_data,
> - req.certs_len)) {
> + if (npages && copy_to(req.certs_address, snp_dev->certs_data,
> + req.certs_len, type)) {
This can also be a single line now.
Thanks,
Tom
> ret = -EFAULT;
> goto e_free;
> }
>
> - if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
> + if (copy_to(arg->resp_data, resp, sizeof(*resp), type))
> ret = -EFAULT;
>
> e_free:
> @@ -653,13 +679,13 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
>
> switch (ioctl) {
> case SNP_GET_REPORT:
> - ret = get_report(snp_dev, &input);
> + ret = get_report(snp_dev, &input, SNP_UARG);
> break;
> case SNP_GET_DERIVED_KEY:
> ret = get_derived_key(snp_dev, &input);
> break;
> case SNP_GET_EXT_REPORT:
> - ret = get_ext_report(snp_dev, &input);
> + ret = get_ext_report(snp_dev, &input, SNP_UARG);
> break;
> default:
> break;
>
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